1. Field of Invention
The present application is generally related to radiation imaging, and more particularly the present application is related to an X-ray imaging apparatus equipped with a novel handle unit.
2. Description of Related Art
X-ray imaging, an imaging technique in which a subject is irradiated with X-rays and a film-screen is used to detect the intensity distribution of the X-rays passing through the subject in order to obtain X-ray image of the object, is well known. Nowadays, the imaging method has been shifted from the conventional film-screen method to a digital radiography (DR) method using an imaging apparatus (a plat panel detector (FPD)) including a plane sensor on which pixels of minute photoelectric conversion elements and switching elements are arranged in a checkered pattern. The advantages of the DR method are that a stable X-ray image is obtained even if the amount of X-ray exposure is varied because the plane sensor in a FPD has a much wider dynamic range than a conventional photosensitive film, and that X-rays can be instantly obtained because chemical treatment is not required.
An X-ray imaging apparatus is categorized into two types: a stationary type that is installed at a predetermined location such as a general imaging chamber, and a portable type that can be carried around. In recent years, a demand for a portable X-ray imaging apparatus (hereinafter referred to as an “electronic cassette”) has increased.
Furthermore, in recent years, a wireless cassette incorporating a battery and an antenna for radio communication instead of a power supply cable has been proposed by patent and non-patent literature documents, and has been made commercially available.
Japanese Patent Application Laid-Open No. 2009-237074 (herein JP 2009-237074), and U.S. Patent Application Publication No. 2010/0054399 (herein US 2010/0054399) discuss a wireless cassette provided with a handle portion to improve portability. In JP 2009-237074, a detachable grip member is provided with an antenna along an outer surface therein. In US 2010/0054399 a handle portion has a notification section that gives notice of an operating state of the radiation detector. Further, U.S. Pat. No. 7,696,722 discloses a detachable handle for a wireless X-ray detector; a power level indicator is provided on the outer surface of the handle. However, if a shielding substance adheres to grip member of the electronic cassette discussed in Japanese Patent Application Laid-Open No. 2009-237074, the strength of a radio wave is lowered; moreover, when the grip member is grasped by the operator, radio communication is blocked. In addition, although a unit for notifying an operator of the state of the electronic cassette is provided on the handle of the electronic cassette discussed in US 2010/0054399, the state notification can covered when the operator grasps the handle. A similar problem exists with U.S. Pat. No. 7,696,722.